The rationale of this Program Project is that spontaneous DMA damage drives major components of the aging process, through direct adverse effects, but more likely by inducing genome maintenance responses, resulting in senescence, apoptosis and/or genomic and epigenomic errors. The long-term objectives of Project 2 are to test the hypothesis that somatic DMA alterations, including genome rearrangements and epigenomic changes, causally contribute to aging by gradually dysregulating gene expression leading to cell functional decline and degeneration and eventually to age-related pathologies, including but not limited to cancer. In Specific Aim 1 of the renewal application we first plan to significantly broaden the scope of the molecular endpoints thus far analyzed. For that purpose, in collaboration with Project 1, we will measure spontaneous DMA damage, changes in CpG island methylation and transcriptional noise levels in tissues of normal and DMA repair-deficient, prematurely aging mice. In Specific Aim 2 we will further study DMA double-strand breaks, as a potentially important intermediate in generating genome instability, dysregulated gene expression and cellular senescence in mouse and human primary fibroblast cultures (with projects 3, 4 and 5). In Specific Aim 3, we propose to combine functional assessment of a single cell with genome-wide analyses of its transcriptome, epigenome and genome. Successful pursuit of these Specific Aims should provide new insight into the role of genome maintenance as a determinant of aging, with a focus on the relationships among various molecular and cellular end points.